Snowplow assemblies are commonly mounted onto a variety of vehicles during winter months for efficiently removing snow from paths, sidewalks, roadways, and other areas. These assemblies commonly employ a blade or moldboard in a forward position. The moldboard is typically mounted onto a plow frame, with the plow frame in turn being mounted onto the front of the vehicle, or one of the sides of the vehicle where the plow is a “wing,” or “benching,” plow. As the vehicle moves forward, the moldboard contacts the snow to displace it to one or both sides of the moldboard, thereby clearing the snow from the surface over which the moldboard passes. Examples of conventional snowplow assemblies are provided in U.S. Pat. Nos. 4,215,494, 5,109,618, 5,121,562, and 5,191,727.
During the plowing of snow, the moldboard is typically positioned so that its lower edge contacts and slides along, or is held just above, the road or other surface being plowed. Of course, roads, driveways, parking lots and other surfaces may be irregular, and may further contain protruding rocks, curbs, man-hole covers, ice chunks, or other debris embedded therein. These irregularities potentially create problems. For example, when the lower edge of a moldboard strikes an irregularity or other immovable object, the force of the impact may damage the moldboard, the frame, or in some cases the vehicle itself.
In order to protect the moldboard, the frame assembly and the vehicle from damage during use, it is known to mount the moldboard, or the lower portion thereof, pivotally so that the moldboard (or lower portion thereof) can “trip,” or move, to avoid fully receiving the impact momentum energy developed when it strikes a rigidly fixed or immovable object. The moldboard can trip to pass over the object to avoid any significant damage to the assembly, truck chassis, driver/operator, etc. After the moldboard passes the object, a biasing force, typically provided by a spring, biases the moldboard back into its normal plowing position.
A “full trip” moldboard version where the entire moldboard pivots in response to encountering an obstruction is shown and described in U.S. Pat. No. 6,073,371 to Goos et al., issued Jun. 13, 2000, for example. In a “cutting edge trip” moldboard version, the moldboard includes a discrete cutting edge portion that is pivotally attached to the remainder of the moldboard with only the cutting edge pivoting in response to encountering an obstruction. Operators often express a strong preference for one version over the other.
While various configurations have been employed for biasing a pivotable moldboard, the biasing force provided by many of these configurations cannot be adjusted and is, therefore, often not optimal for more than one set of operating conditions. This creates a problem when a vehicle is assigned to remove snow from a variety of surfaces and driving speeds, each having a different surface condition, or in changing environmental conditions.
Some snowplow assemblies are assembled with a large hydraulic press which imparts a “preload” bias force on the springs, i e., the spring is preloaded with a selected amount of spring potential energy. The removal and/or replacement of an installed spring having a preload force imparted thereon can be very dangerous.
In other cases, preloaded springs for use in snowplows have been shipped in a cage or a container. In the event that a preloaded spring develops a structural defect, such as a stress fracture, or breaks its packaging while being handled, the chance for a serious injury occurring can be very great.
While there exist some snow plow assemblies that do provide for some degree of adjustment of a biasing force, these assemblies can be complicated mechanically and not relatively easily and quickly adjustable by a vehicle operator after the vehicle leaves the garage. For example, threaded bolts are used to adjust the spring preload in some snowplow assemblies. In these assemblies, the preload tension imparted upon the moldboard is often adjusted by the movement of threaded bolts. Such adjustment can be difficult and slow because the bolts are susceptible to rusting which can make them hard to turn or can “freeze” the bolts in place. Furthermore, in some instances, the operator may feel it is necessary to remove the moldboard from the snowplow drive frame to improve the accessibility to the bolts, thereby increasing the time required for the adjustment process and making it less likely that such an adjustment would occur in the field. Often, it is desirable to change the preload force imparted upon the moldboard in the field, as road surface conditions vary, such as when the vehicle moves from a paved surface to an asphalt or gravel surface, for example.
Thus, there exists a need for a snowplow assembly that overcomes the aforesaid and other problems associated with existing assemblies. One such need is for a snowplow assembly which provides an easily-mounted and readily-adjustable trip mechanism. Another need is for a trip mechanism that can provide for safe installation and removal.